Inductive charger and charging method

Abstract

A charger for inductively charging one or more battery powered appliances simultaneously includes an external unit configured to inductively provide power to the battery powered appliances. The external unit includes two or more primary coil pairs that are arranged in a circular pattern; an AC power source for providing an alternating current (AC) to the primary coil pairs for generating a rotating magnetic field between respective primary coils of the primary coil pairs; and a processor for driving the AC power source. The one or more battery powered appliances are configured to be arranged inside the circular pattern of the external unit. Further, each appliance includes a secondary coil for enclosing part of the magnetic field and, in response, generating a current for charging the battery of the appliance.

The invention claimed is: 
     
       1. A charger apparatus comprising:
 one or more appliances, each appliance being powered by a battery and comprising a secondary coil for generating a current for charging the battery; and 
 a charger comprising a plurality of primary coil pairs arranged in a circular pattern with coils of each pair positioned opposite each other, each primary coil pair including one or more switches for short circuiting the respective primary coil pair, the circular pattern enclosing the secondary coils of the one or more appliances placed in the charger; 
 wherein, when an alternating voltage is provided to the plurality of primary coil pairs, a rotating magnetic field between respective primary coil pairs of the plurality of primary coil pairs is generated thereby inducing current in the secondary coils. 
 
     
     
       2. The charger apparatus of  claim 1 , further comprising a processor for driving the AC power source, wherein the processor is configured to short circuit at least one of the plurality of primary coil pairs using the corresponding switches, and to supply the alternating voltage to remaining of the plurality of primary coil pairs. 
     
     
       3. The charger apparatus of  claim 1 , further comprising four primary coil pairs. 
     
     
       4. The charger apparatus of  claim 1 , wherein the alternating voltage has a frequency of about 10 kHz or more. 
     
     
       5. The charger apparatus of  claim 1 , wherein the magnetic field is rotated at a frequency that is more than 1000 times below a frequency of the alternating voltage. 
     
     
       6. The charger apparatus of  claim 1 , wherein the alternating voltage is provided at a frequency that substantially corresponds to a resonance frequency of the one or more appliances. 
     
     
       7. The charger apparatus of  claim 1 , further comprising a cover of high magnetic permeability material that encloses the plurality of primary coil pairs. 
     
     
       8. A method to inductively provide power to appliances, the method comprising the acts of:
 providing or more appliances, each appliance being powered by a battery and comprising a secondary coil for generating a current for charging the battery; 
 arranging a plurality of primary coil pairs in a circular pattern with coils of each pair positioned opposite each other, each primary coil pair including one or more switches for short circuiting the respective primary coil pair, the circular pattern enclosing the secondary coils of the one or more appliances; 
 providing an alternating voltage to the plurality of primary coil pairs; and 
 generating a rotating magnetic field between respective primary coil pairs of the plurality of primary coil palm thereby inducing current in the secondary coils. 
 
     
     
       9. The method of  claim 8 , further comprising the acts:
 short circuiting at least one of the plurality of primary coil pairs; and 
 supplying the alternating voltage to remaining plurality of the primary coil pairs.